1. Field of the Invention
The present invention relates to fluid flow control apparatus.
2. Description of the Prior Art
British patent specification No. 2,124,338 discloses pillar tap incorporating a fluid flow control system in which the pressure of water is used to assist the opening and closing of the tap.
In particular an isolated chamber is provided with an opening in which is mounted a flexible diaphragm carrying a valve member for controlling the flow of water from the tap. By allowing the entry of water into the chamber the valve member can be urged by the resultant increase in pressure in the chamber, into contact with a main valve seat to shut off the tap. By releasing water from the chamber the pressure in the chamber is reduced and the valve member can be forced by the pressure of the water supply acting n that part of the valve member not shielded by the valve seat, away from the valve seat to allow the flow of water from the tap.
Once the chamber is sealed the gap between the valve member and valve seat will remain substantially constant and any fluctuation in the pressure of water supplied to the tap will be manifest by a change in the rate of flow of water from the tap. If the water in the sealed chamber contains entrained air bubbles then the gap between the valve member and the valve seat will vary with changes in water pressure but in such a sense as to amplify the changes in flow rate. Such fluctuations in flow rate are undesirable particularly when the tap forms one of a pair of taps used in a hot and cold water mixing arrangement.
It is an object of the invention to provide an improved tap.